After a tough workday, workout, or you just feel achy and stiff, try a Robax Heatwrap with Thermacare Technology to provide your back and hips up to 16 hours of pain-relief. Each Robax Heatwrap Lower Back/Hip contains 6 single use wraps that provide deep penetrating therapeutic heat to help relax and soothe sore, achy muscles with 8 hours of heat and another 8 hours of relief after you take it off. The combination of ingredients in a Robax Heatwrap react when exposed to oxygen, causing the wrap to heat up. Easy to wear underneath clothing, too and nobody will know but you.